The present invention relates especially to drives, for instance for backrests or window panes of automotive vehicles, in which a reciprocatably tiltable driving arm is to be coupled with a turnable adjusting member during tilting movement of the driving arm in one direction and in which the driving arm free wheels with respect to the adjusting member during tilting of the arm in the opposite direction.
The German Auslegeschrift No. 1,142,767 discloses an articulated mount for motor vehicle seats in which the inclination of the backrest relative to the seat part is adjustable by a threaded spindle arrangement which may be driven in a selective direction over a free wheeling arrangement. The free wheeling drive comprises a gear serving as the adjustable member and a double pawl tiltably mounted on a driving arm, which in turn is mounted tiltable about the axis of the adjustable member, in which the double pawl is held by a compression spring in one or in another position in which it takes the adjustable member along in one or the other direction during tilting of the driving arm. The adjustment of the double pawl to one or the other position is carried out by means of a linkage which is actuated by means of a grip member, shiftably mounted on the driving arm. In arrangements of this kind a ratching noise will result during the idle stroke of the driving arm which is caused during movement of the pawl over the teeth of the adjustable member.
The same disadvantages are inherent in an actuating device for a hinge fitting in an automotive vehicle as disclosed in the German Pat. No. 1,925,778, in which during movement of the driving arm in one or the other direction only half of the available tilting angle of the driving arm is used. This construction is likewise provided with a tiltable pawl on the driving arm, which, during the idle stroke of the latter, ratches over the teeth of the adjustable member.